The present invention relates to an apparatus and method for determining a failure of an air induction system of an internal combustion engine.
There is provided an air flow sensor (AFS) as an apparatus for detecting an induction air volume induced into an internal combustion engine (engine). When a disconnection of a circuit of the air flow sensor or a failure regarded as a characteristic abnormality thereof occurs, an error in detecting an induction air volume is caused, and this is attributed to the deterioration of exhaust emissions (exhaust gas). Thus, the air flow sensor needs to be monitored to see if there exists a failure.
The Examined Japanese Patent Application Publication No.Hei02-55616 describes a technique in which a failure of the air flow sensor is determined by comparing a calculated induction air volume from an output of the air flow sensor with a failure determination value set in such a manner as to correspond to the opening position of a throttle. In addition, the Japanese Patent No. 3047589 describes a technique in which a failure diagnosing area is set in correspond to the pressure in an air induction pipe.
Since the AFS failure detection approaches according to the related arts described above are such as to utilize a special driving area such as an area which is free from fluctuations in the load and rotational speed of the engine, the approaches encompass a problem that the detection frequency is reduced. An object of the invention is to provide a failure detection method which can relax the limitation on the driving area where an AFS failure detection is carried out to thereby increase the frequency at which a failure detection is carried out.